Card that works in validator preview is rejected from whitelist



I’m trying to add a Summary Card with Large Image to a blog on a site hosted on Squarespace. The site uses Open Graph already, so I’m using a combination of those tags and custom Twitter tags like the bottom example on

The card looks good in the validator’s preview (try out this page, for example), and nothing bad shows up in the logs, except for the fact that the site isn’t on the whitelist. Here’s a picture:

But, when I request approval for whitelisting, the site is rejected within a minute. The email says,

The URL you provided for to use the summary_large_image card did not validate. Please make sure the page contains valid metadata, then reapply for a Twitter card.

I tried re-requesting approval and adding all the custom Twitter meta tags instead of relying on Open Graph, but same problem. How can I figure out what is going wrong?